1. Field of this Invention
This invention relates to a range limiter for thermostats, especially thermostats for room-temperature control.
2. Prior Art
In the normal operation of a thermostat, the operating set-point is manually established by adjusting a control member to a desired temperature. The heating apparatus of the room will deliver heat when the temperature drops below the set temperature and the heat will be cut off when the temperature reaches or exceeds the set temperature of the thermostat. The occupant of the room adjusts the control member to establish different set-points. Poorly informed people are tempted to adjust the thermostat incorrectly. Thus, if the room temperature is below the desired temperature, an occupant may adjust the member to a grossly excessive temperature setting, hoping that the room temperature will rise faster. The room temperature rises to the desired temperature and continues rising until the temperature is well above the desired level. Then the occupant (if present) must adjust the thermostat to a lower setting. Once the room temperature is higher than desired, the temptation exists for the occupant to adjust the thermostat well below the desired temperature with the thought that such adjustment will cause the temperature to drop faster. Under such a low thermostat setting, the heater does not turn on until the room temperature drops to an excessively low level. Once again the occupant is unhappily exposed to an uncomfortable temperature.
In an effort to contend with this problem, thermostats often have range-limiting devices. Either a high-limit stop or a low-limit stop has been provided, and in some instances both high and low stops or range limiters have been provided. The arrangements are usually complicated and add significant cost. When a range limiter is provided, the adjustment is restricted to a modest latitude so that, even where an inexpert user is involved, the extent of misadjustment is limited. Accordingly, the consequences of improper adjustment, as set forth above, are minimized. Range limiters are particularly valuable (for example) in motels and other places of public accommodation, because it is not practical to indoctrinate each new guest into the proper use of his room thermostat.
Prior art range limiters are divided into two classes. One class involves a range limiter mounted externally of the thermostat structure. This allows the occupant or guest to readily notice the range limiter and to manipulate or remove it, thereby defeating its purpose. The second class involves a range limiter mounted internally within the thermostat structure. This class of range limiters is permanently or semi-permanently mounted, so that they cannot be replaced with a limiter having a different range. This class also does not involve adjustable means for easily adjusting or changing the range. Further, this class of range limiters often involves a physical deforming or removal of part of the range limiter that makes range changing difficult or impossible using the same permanently (or semi-permanently) mounted range limiter.
Attention is drawn to U.S. Pat. Nos. 1,238,557, 1,348,841, 2,385,823, 2,562,425, 2,813,938, 3,011,039, 3,086,092, 3,121,151, 3,670,284, 3,771,387 and 3,807,254.